Heretofore, there is a case that a door, a body exterior panel, and others of an automobile are mounted with a vehicular resin component such as a side mudguard for enhancing design quality and functionality. The vehicular resin component is, generally, an injection-molded component formed by injection molding. Therefore, in most cases, a mounting seat for mounting the vehicular resin component to the door, the body exterior panel, and others of the automobile is integrally formed with the vehicular resin component in injection molding. As a structure of mounting the vehicular resin component to the door, the body exterior panel, and others, it has been generally known a clip engagement structure in which a clip is fitted in a mounting seat of the vehicular resin component and a locking hole is formed in the door, the body exterior panel, and others and the clip is engaged in the locking hole (see Patent Document 1, for example).